The Ha'Yom Yom of 17 Teves says that we don't learn on nittel nacht (Dec. 24 at night,C. eve), in order not to increase chayus-vitality [to kelipa].

The Rebbe Rashab said that he doesn't hold of those masmidim who can't forego those eight hours (bec. it's only until midnight that you don't learn).

This custom (if that's the right word for it) of not learning on nittel nacht is very different than other customs we have that differ from those of non-Chassidim. Because whether you light the menora in the window or doorway, or eat gebrochts or not, is nothing like saying that learning Torah at that time, increases the vitality of kelipa.

What irks non-Chassidim about this is that we are saying THIS IS THE METZIUS. Whether or not you ACCEPT it, doesn't CHANGE the reality, that your learning at that time increases the vitality of kelipa!

In other words, it doesn't just increase the vitality of kelipa for those who believe it does!

are u sure? in shaarei halacha uminahag vol. 3 p. 67, it says that there is no nitel in israel, and it says a reason, see there. also see lekutei sichos vol. 15 that Jews living in arab countries don't have the minhag of nitel.

nitel is nohug in E.Y. -I was once learning in shikun chabad and forgot that that night was nitel, and Subbota himself reminded me!- there are various reasons for nitel , some al pi nigleh and some al pi "inyonim". A good source for anyone interested in the various minhagim and reasons is Nitei Gavriel

In the Litvish world they dont know about nittel, in seforim that copile this things as Nitei Gavriel and Hanitel, the GRA'sname does not appear as a source, in seforim on GRA Aliyos Eleyuhu, Masseh RAV they dont know about so in all likelyhood it did not happened.

see Igros Kodesh, volume 14, p. 352 - a letter about nittel nacht, in which the Rebbe says, "it seems to me that each country should follow the secular calendar of that country, and if there are different customs then they should observe the night that most goyim celebrate"

However, different groups refrain from learning for different reasons, so if another group does it for a different reason than Lubavitch, then it might come out different than the Igros Kodesh, v'chol echod lifi minhogoy.(other groups should follow their own minhog)